i B, HCLAKUSEON@Y erat i a" pa Thermal Radiation - Flash and Heating Effects Background Information Levels of thermal radiation that can produce skin burns are limited to the immediate testing site areas. Effects on the eyes, however, may extend for much greater distances. These effects may be either permanent damage to part of the eye or a temporary flash "blindness." The latter is only a discomforting effect but can be potentially hazardous in the case of automobile drivers and aircraft pilots. This is one of the reasons why certain areas of highways have been closed for specified periods of time around the Nevada Test Site and also why the same precautions have been taken for the air lanes around the Nevada and Pacific testing sites. Perhaps surprisingly, the amount of heat (calories) received per unit area on the rear portion of the eyeball (retina) does not decrease with increasing distance from the point of burst - except for the absorption (attenuation) effect in the atmosphere. While the expected decrease in energy per unit area occurs all right outside the eye (the inverse square law), the image formed on the retina decreases correspondingly in the same proportion. The result is that the thermal dose (in calories per unit area) remains constant though overasmaller area on the retina. This reduction in image size on the retina/increasing distance from the burst continues until it reaches approximately 0.00025 inches (10 microns) in diameter which is generally taken as about the diffraction limit for the human eye, i.e., light waves will bend slightly as they pass through a small opening such as the pupil of the eye. Of course a dilation of 29 CIAL USE-ONLY 34